Network Paradox Part III: The incredibly shrinking cellular network
In Part I and Part II of this series, we established how cell sizes will have to shrink to meet data capacity demands. In Part III we examine just what those small cells will look like
See Part 1 of the Network Paradox, Mobile Data Demand by the Numbers, and Part 2, Meeting the Mobile Data Demand. All three stories are part of Connected Planet’s Mobile Data Paradox interactive feature and microsite.
There’s no question about it: If the mobile broadband network is going to support the enormous traffic loads the industry is anticipating, it will have to shrink. In order to scale traffic loads upwards, the size of cells have to scale downwards. Even with more efficient technologies and gobs of new spectrum, re-use of the current frequencies will be a major component of meeting mobile demand in the future. And while no carrier, vendor or regulator will argue that point, there’s little consensus over what those small cell architectures will like and when they must be implemented.
Small cells aren’t exactly a new concept for the wireless industry. Operators have been drawing in their cell radii since the advent of analog systems. As higher frequency bands have come online, operators have been forced to build tighter clusters of cells to deal with those frequencies’ lower propagation characteristics. As penetration has increased in urban areas, more towers have gone up to meet the needs for capacity as well as the need for coverage. Operators have dabbled in microcell and picocell architectures, deployed remoter radio heads and distributed antenna systems.
Ultimately, though, the macro cellular topology of wireless networks has remained unchanged. Spot coverage aside, the typical wireless network remains a collection of large microcells transmitting from towers and rooftops. That topology will have to change. The macro-cellular network won’t disappear, but industry experts believe it will become an umbrella coverage network, under which hundreds of thousands of much smaller cells will carry the burden of the mobile data explosion.
Just how small will those cells be? If technology and cost were not a factor and operators did nothing to curb the ever increasing consumer and enterprise hunger for bandwidth, there really isn’t a limit, said Rupert Baines, vice president of marketing for PicoChip.
“The logical endpoint is that the cell should be the size of a person,” Baines said. “Everyone should have their own bubble of coverage. We’re obviously looking at something more pragmatic.”
PicoChip’s more pragmatic approach is taking an already common home coverage solution, the femtocell, and optimizing it for the wide area network. Femtocells today are essentially private network coverage solutions. They use an operator’s spectrum, but they connect to the network via a customer’s broadband line. They only support a few connections at one time, and only pre-authorized devices can access them. That hardly seems the ideal platform for expanding the public mobile data network.
But Baines explained that femtos are designed as private home base stations because they were originally intended to be coverage solutions, bringing voice access to homes and businesses the wide area network had trouble reaching. As network capacity emerges as the operator’s most pressing need, the femto is being redesigned as a capacity platform, Baines said. PicoChip’s latest round of femto silicon meets the local area base station (LABS) standard for use in a wide area deployments, supporting 64 simultaneous data connections and the background signaling traffic for 400 simultaneous smartphones. The femto isn’t restricted to the devices of a particular home or business, and it can be toughened up to meet the needs of an outdoor public network deployment. Such a femto may not carry the sub-$200 price tag most home femtos are going for today, but even at a premium cost the economies of scale for such off-the-shelf base stations are enormous, Baines said.
“They’re what microcells would have been if operators had actually deployed them and what picocells should have been when they were first designed,” Baines said. “The capex works out so that you can add lots and lots of small base stations for much less than the cost of adding a single macro cell.”
There’s no question about it: If the mobile broadband network is going to support the enormous traffic loads the industry is anticipating, it will have to shrink. In order to scale traffic loads upwards, the size of cells have to scale downwards. Even with more efficient technologies and gobs of new spectrum, re-use of the current frequencies will be a major component of meeting mobile demand in the future. And while no carrier, vendor or regulator will argue that point, there’s little consensus over what those small cell architectures will like and when they must be implemented.
Small cells aren’t exactly a new concept for the wireless industry. Operators have been drawing in their cell radii since the advent of analog systems. As higher frequency bands have come online, operators have been forced to build tighter clusters of cells to deal with those frequencies’ lower propagation characteristics. As penetration has increased in urban areas, more towers have gone up to meet the needs for capacity as well as the need for coverage. Operators have dabbled in microcell and picocell architectures, deployed remoter radio heads and distributed antenna systems.
Ultimately, though, the macro cellular topology of wireless networks has remained unchanged. Spot coverage aside, the typical wireless network remains a collection of large microcells transmitting from towers and rooftops. That topology will have to change. The macro-cellular network won’t disappear, but industry experts believe it will become an umbrella coverage network, under which hundreds of thousands of much smaller cells will carry the burden of the mobile data explosion.
Just how small will those cells be? If technology and cost were not a factor and operators did nothing to curb the ever increasing consumer and enterprise hunger for bandwidth, there really isn’t a limit, said Rupert Baines, vice president of marketing for PicoChip.
“The logical endpoint is that the cell should be the size of a person,” Baines said. “Everyone should have their own bubble of coverage. We’re obviously looking at something more pragmatic.”
PicoChip’s more pragmatic approach is taking an already common home coverage solution, the femtocell, and optimizing it for the wide area network. Femtocells today are essentially private network coverage solutions. They use an operator’s spectrum, but they connect to the network via a customer’s broadband line. They only support a few connections at one time, and only pre-authorized devices can access them. That hardly seems the ideal platform for expanding the public mobile data network.
But Baines explained that femtos are designed as private home base stations because they were originally intended to be coverage solutions, bringing voice access to homes and businesses the wide area network had trouble reaching. As network capacity emerges as the operator’s most pressing need, the femto is being redesigned as a capacity platform, Baines said. PicoChip’s latest round of femto silicon meets the local area base station (LABS) standard for use in a wide area deployments, supporting 64 simultaneous data connections and the background signaling traffic for 400 simultaneous smartphones. The femto isn’t restricted to the devices of a particular home or business, and it can be toughened up to meet the needs of an outdoor public network deployment. Such a femto may not carry the sub-$200 price tag most home femtos are going for today, but even at a premium cost the economies of scale for such off-the-shelf base stations are enormous, Baines said.
“They’re what microcells would have been if operators had actually deployed them and what picocells should have been when they were first designed,” Baines said. “The capex works out so that you can add lots and lots of small base stations for much less than the cost of adding a single macro cell.”
Alcatel-Lucent head of global wireless marketing and strategy Jean-Pierre Lartigue won’t argue against the utility of femtocells in the network of the future, but he also doesn’t view the femto as the sole answer to solving the capacity crunch. The network won’t merely take two shapes, alternating large cells and tiny ones. Instead it will have a much greater variety of shapes with cells of all sizes mingling and overlapping to address the individual capacity needs on any given area, Lartigue said.
Alcatel-Lucent is obviously a big builder of macro cellular base stations, and recently it has built up one of the industry’s largest femtocell businesses. But it has also developed every manner of cell size in between, each designed to target a particular capacity scenario. Traditional private business and home femtos will co-exist with public indoor and outdoor femtocells—solutions that scale from an individual customer’s home to malls and outdoor squares. But data capacity demands are permeating the entire network, not just those areas where we’d traditionally stick a Wi-Fi hotspot, Lartugue said.
Alcatel-Lucent is developing what it calls a metro cell, which is designed to be deployed across the urban landscape. They would form an underlay network beneath the macro-cellular umbrella, adding many multiples of coverage to the existing macro footprint at much smaller cost than adding more macro carriers, Lartigue said.
The logic of the femto still applies: it’s much cheaper to increase capacity available to users in homes or businesses through deploying multiple femtocells than installing a new carrier that would blanket those homes. “We’re bringing the capability of the femto to the metro network,” Lartigue said. “The macro network remains in place. You can’t discount it. But at certain point you have to cap the macro network. The cost of adding capacity through the macro network becomes too high.”
Each metro cell has the same capacity as a full macro cell, just within a much smaller area. Adding four metro cells within a macrocell’s radius would increase capacity available to that area by four times. Adding 16 cells would increase that same marco cell’s capacity 16 times. But because the cells are smaller, propagation becomes a big additive factor. The closer a user is to the center of a cell the better connection and faster speeds they receive. By creating network with many more cell centers, not only does the overall theoretical capacity of the network increase, but the amount of that capacity available to customers also increases.
In terms of efficiency, it would be theoretically 100 times cheaper to send a bit through a small cell than through a macro cell due to the high level of frequency reuse in such topologies, Lartigue said. When factoring deployment, infrastructure, backhaul and operational costs, that number falls considerably, but Lartigue estimates that an operator can save 60% to 70% on the cost of adding new capacity to network through small cells.
3G metro cells would have to run over separate spectrum from the macro network due to interference, but with 4G technologies metros could use the same spectrum due to long-term evolution’s (LTE’s) interference cancellation capabilities. That’s probably one of the principle reasons why operators aren’t deploying smaller cell architectures today. 3G spectrum is a scarce commodity, and unless an operator were to roll out a massive-scale small cell deployment, they couldn’t afford to take a full 3G carrier offline.
In addition, operators are now upgrading their 3G networks or deploying 4G networks, which promise to bring a huge quantity of capacity online immediately. But those capacity improvements won’t be near enough to handle a 40X increase in traffic.
“Overlaying 3G and 4G architectures with only get you three or four years out,” Lartigue said. “You can add more towers and more carriers, but there is a limit. In two or three years, we will pass that threshold where adding capacity to the macro network doesn’t make cost sense anymore.”
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